Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Derivative [Line Items]
Notional Amount	$ 377,980	$ 364,927
Asset Derivatives
Derivative assets, gross amount offset	(321)	(154)
Derivative assets	149	175
Liability Derivatives
Derivatives liabilities at fair value	(225)	(168)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	4,000	4,500
Cash collateral received for derivative instruments	47	5
Total risk management derivatives designated as hedging instruments
Derivative [Line Items]
Notional Amount	291,308	285,437
Asset Derivatives
Derivative assets, gross amount offset	(321)	(154)
Derivative assets	53	83
Liability Derivatives
Netting adjustment	4,241	4,662
Derivatives liabilities at fair value	(61)	(24)
Total risk management derivatives designated as hedging instruments | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	36,274	38,858
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Total risk management derivatives designated as hedging instruments | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	255,034	246,579
Asset Derivatives
Derivative assets, gross	374	237
Liability Derivatives
Derivative liabilities, gross	(4,302)	(4,686)
Pay-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	8,269	5,582
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	125,372	97,808
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	28,005	33,276
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	120,583	99,799
Asset Derivatives
Derivative assets, gross	54	1
Liability Derivatives
Derivative liabilities, gross	(4,097)	(4,525)
Basis | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	250	41,250
Asset Derivatives
Derivative assets, gross	8	25
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign currency | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	303	300
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(98)	(98)
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	5,816	5,286
Asset Derivatives
Derivative assets, gross	294	204
Liability Derivatives
Derivative liabilities, gross	(35)	(18)
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	2,666	2,136
Asset Derivatives
Derivative assets, gross	18	7
Liability Derivatives
Derivative liabilities, gross	(72)	(45)
Futures | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	44	0
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Mortgage commitment derivatives
Derivative [Line Items]
Notional Amount	60,205	55,706
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	51	89
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(150)	(78)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional Amount	3,593	2,596
Asset Derivatives
Derivative assets	2	4
Liability Derivatives
Derivatives liabilities at fair value	(16)	(8)
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional Amount	17,550	17,808
Asset Derivatives
Derivative assets	2	50
Liability Derivatives
Derivatives liabilities at fair value	(111)	(57)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional Amount	39,062	35,302
Asset Derivatives
Derivative assets	47	35
Liability Derivatives
Derivatives liabilities at fair value	(23)	(13)
Credit enhancement derivatives
Derivative [Line Items]
Notional Amount	26,467	23,784
Asset Derivatives
Derivative assets	45	3
Liability Derivatives
Derivatives liabilities at fair value	$ (14)	$ (66)